In electrically-driven pumps, and regardless of whether the pump is a vacuum pump, a compressor or a fluid circulator, the functions of electrical drive and of pumping are provided by juxtaposing two essentially independant units which are interconnected by a mechanical coupling, or which share a common shaft. Such an arrangement does not favour the provision of a compact unit.
Preferred embodiments of the present invention are compact, and as a consequence, they are often cheaper than prior units of similar performance.